There is evidence that implicit and explicit processes may represent neurophysiologically and functionally distinct memory systems. The purpose of these studies is to test this proposal by using electrical potentials recorded from the brain to compare implicit and explicit memory processes in young and old controls, and patients with Alzheimer's disease. Automatic and effortful memory processes will be studied by comparing implicit and explicit memory tasks. Implicit memory processes result in the facilitation of performance and brain potentials but do not necessarily require conscious recollection. Explicit memory processes require conscious remembering . Behavioral studies have suggested that more automatic or implicit memory functions such as priming may be preserved in patients who show impairment on effortful or explicit memory tasks such as recognition. Priming occurs, for example, when the prior presentation of a word facilitates the response to that word on second presentation, without the need to remember the prior study experience. Furthermore, within explicit memory, a more automatic familiarity component of recognition may be preserved even after the more effortful retrieval component becomes impaired. This research will use event-related potentials and behavioral techniques (reaction time, accuracy) to quantify the differences between priming compared to recognition and define the brain mechanisms involved in controls, and test difference between patients and controls on these tasks. An added benefit of the use of event-related potentials is that implicit memory can be tested even in patients who cannot respond to the task. A target detection task will test effects on implicit memory when no response is required to repetitions, but when subjects are instead asked to press a reaction time button to rare target words. Implicit memory also will be examined to incorrectly identified "new" and "old" words. Differences in topographic distribution suggest different sources in the brain are contributing to the brain potentials recorded to a particular ADMINISTRATIVE NOTES: The Committee judged the application to be appropriate for inclusion in priority category of newer, less experienced investigators.